My Barn Twins

When I first started looking at this bike, I knew nothing about an airhead. I could see that the air inlet and filter must be hidden somewhere inside that metal case on the engine, and I could make out the drive train, but it all looked kind of mystical.

Then, when I actually got the bike, I started reading about it (Duane Ausherman, Snowbum, MOA, and of course all you inmates). Now I have read so much that I am a shore 'nuff expert! Just ask me.

The same friend who gifted me with a membership to the MOA gave me all his back issues of BMW Owners News. He said he didn't care what I did with them -- he was just clearing stuff out. This was a stack of magazines about 1 1/2 feet tall, going back to January, 2009. I actually read all of them over a period of time. Then I went back through and tore out the articles most useful to me. That would be all the Matt Parkhouse and Paul Glaves articles, along with some other stuff. The rest I put in the recycle bin. With the stuff I saved, I made up a 3" inch binder and typed up an index. There is a lot of good info there for sure.

I also sent off for some service manuals -- one is a reproduction of the FSM and the other is Clymer. I'd rate them both as "marginal" and I don't take anything they say at face value without a lot of internet reading, but it's helpful to have them both.

In case anybody is interested, here's my take on the service manuals.
Of the two, the Clymer Manual is more readable and far more detailed. It has a few problems and mistakes, but it is generally much more usable than the factory manual. I don't have the Haynes Manual, but I have one for my Triumph and don't use it at all. If anybody is actually reading all this and thinks the Haynes book is worthwhile, please let me know and I'll probably get one. I need all the help I can get.

The FSM is very bare bones, to say the least. It came in a binder that was too thin, so I had to get a wider one to keep the pages from tearing. It shows a general picture for each procedure and maybe a picture of any special tools required. The numbers seem to be O.K. if you stick with the metric units and convert to inch units on your own if you so desire. The Germans included the inch figures in parenthesis, but most are incorrect.

As just one example, they listed the R90 bore size as 90.00 (3.5100). The problem is that 90.00mm actually equals 3.5433", so they were wrong by an error of .0333", which is a mistake equaling more than 1 1/2 times the allowable amount for the first overbore!

Instead of using the correct conversion factor where 1 inch = 25.4mm exactly, they used 26.64 fairly consistently (at least on that page of the book). Where did that come from??!

They also followed the corollary of Murphy's Law which says to always state your data in the least usable units, such as furlongs per fortnight as opposed to miles per hour.

By this, I mean that they give torque values in mkp, which stands for meter kilopond, a unit that has not been officially used since 1977. Later books, I assume would express their torque values in Newton Meters. In any case, where they converted torque values to pound feet (many now express torque in foot pounds), their numbers are not to be believed or trusted.

On that note, BMW didn't just have math problems when they wrote their service manual. I was kind of shocked that they put an incorrect sticker on the rear fender, under the seat, that has misplaced decimal points.

Instead of 1mm being equal to about .04" (which it is), they got mixed up and thought that 1mm was about equal to .40". This led to the sticker that tells the rider that he is legally required to have at least .4 inch minimum tread depth. You are not likely to see that much tread on a brand new tire.

Then they went on to say that they recommend at least .8 inch tread depth for speeds up to 80 mph. The next line they got correct, but that made the previous line look more ridiculous. Anyway, you get the idea. It's pretty strange that a company renowned for their fine engineering would let something like this slip through the cracks. Here's a picture of the fender sticker:

Hi David, I hope your bikes are doing well. I've been enjoying the pictures you have posted.

Rub 'n Buff is not exactly paint. It is a very finely ground metallic powder in a carnauba wax base. It is available on-line from a number of sources, as well as in a lot of arts and craft stores. I bought a small tube at Hobby Lobby ($6.00 for 1/2 ounce) which sounds like a lot. That would be enough to do two or more complete BMW engines and transmissions.

I experimented with several different cleaners/polishes, including Simple Green, Zep Brightener, Zephyr Metal Polish, Mother's Metal Polish, Autosol Cleaner, Autosol Metal Polish. I tried several different tools, including Scotch-Brite, brass bristled hand brushes, toothbrushes, small cloth "mops" of different sizes (some in my electric drill, some in my Dremel Tool).

I stayed away from steel wool because various people on the internet advised against it. Yet, some say it works well for them. The fear is that small bits of the wool get imbedded in the alloy and later cause rust streaks. I have my doubts, but I still didn't try it.

What seemed to work best for me with the least elbow grease was the little round brass cup brushes in my Dremel, used with WD-40. Brass rotary brushes alone will turn the alloy yellow, but won't do that when used with WD40. These brushes are small enough to clean in the tighter areas, but do well out on the bigger surfaces too. The brushes are made by Forney, and my local Ace Hardware sells them. They are also available on-line. The ones with the 1/8" shank fit the Dremel Tool.

On a high rpm, the brush almost flattens out, and tends to lose bristles. That is messy and the brush won't last long that way. I was using them at low speed with the surface having just a little WD-40 on it. The brush will last quite a while that way. I scrubbed a small area till it had a lot of black grunge floating up in the WD-40 film. Then I wiped it good with paper towels, and did it again. I repeated this till the black grunge quit showing up. I went through lots of paper towels, but less than one can of WD-40.

When I thought I had it cleaned, I rubbed in a tiny bit of Silver Rub 'n Buff. I think their Pewter color is a better match for what most people think the BMW alloy should be, but I used what I could find without too much trouble.

All it takes is the very slightest amount of Rub 'n Buff to spread over quite an area. Lots of people sneer at it as "makeup for bikes", but it does hide a lot of sins, and it is reversible if you don't like it. Basically it gets down into the smallest pores of the surface and colors them silver or pewter instead of dirty black.

Here are some pictures of the airbox clamshells off my engine:

As found:

One side cleaned:

With Rub 'n Buff:

This picture makes them look shiny because of the lighting. They are not quite like that in normal conditions. They are still shinier than many would like. As I said earlier, you can dull the surface by applying the Rub 'n Buff and not polishing with a cloth.

Note the brake and clutch levers in this picture. I did not use any Rub 'n Buff on them. They were cleaned and polished with AutoSol. There is a lot of variation in the alloy used for different parts of the airhead engine. The Rub 'n Buff helps even things out.

The argument is, "What is the natural color?" To know that, I'd have to ask, "Under what conditions?" For some people, battleship gray is the natural color, because that's what it will all look like eventually if left alone.

Thanks for the encouragement, Cogswell and Wirespokes. I'm sure I'll have some questions for you guys with the high post count once I get this thread caught up with where the bike is now.

The frame and some other parts have been powdercoated. I unwrapped all the smaller pieces and the quality looked very good to me. Based on that, I left the main frame and rear sub-frame wrapped up for now just to protect them. I'll get some pictures up before too long.

Thanks.
I never used rub n buff.
I use wd40 and small wire brushes, etc.
Many of y'all would think that my bike is a filthy pig.
"I do not even have a garage.......you can call home and ask my wife...."
Have a nice day.

Thanks.
I never used rub n buff.
I use wd40 and small wire brushes, etc.
Many of y'all would think that my bike is a filthy pig.
"I do not even have a garage.......you can call home and ask my wife...."
Have a nice day.

Click to expand...

Yeah, but you probably enjoy riding it -- maybe more than if it were all shiny. Sometime I'd like to find a rusty crusty bike and just get it mechanically sound and use it like that in any kind of weather. Something pretty old, and maybe British seems like it would be a lot of fun to have. Not necessarily a rat bike, but something close. I missed a good opportunity with this airhead. Sometimes I don't know what drives me to do what I do. I'm sure I could enjoy a bike like that.

My alloy scrubbing went on seemingly forever. When that got too boring, I'd look for something else to do.

With the engine on the stand, it is basically a six sided rectangular block and there is something to do to each of the six faces. I started at the back by taking the clutch apart.

It all looked good except for the diaphragm spring. I put it on a glass topped table and measured the height of the fingers to the table. The spec is 19.0 +/- 0.5mm, with a max variation of .3mm -- mine averaged 17.3mm and had .4mm variation.

My clutch disc looked good though. Spec is 6.00mm, and min thickness is 4.50mm -- mine was 5.79mm thick at the outer perimeter and 5.83mm near the inside of the friction material, so only .04mm variation and close to new spec.

I started out by ordering parts from Bob's BMW and have found no reason to go anywhere else. They have had almost everything in stock. When they didn't, they would e-mail to ask if I wanted the rest of the parts or if they should wait till it was all there. Their fiche works well, and the parts people are happy to answer questions on the phone.

So, I ordered a clutch spring and some other stuff. When I got the new one, I checked it like I did the old one. I found it at 18.4mm with variation of .1mm -- much better than my old one, but 18.5mm is the bottom end of the tolerance spec. When I called the parts guy at Bob's, to ask if I could exchange for something more in the middle of the spec, he put me on hold and went to their shop area. He got a tech to measure a number of springs from the parts bin. He came back told me that it looked like I had gotten the best one they had. The others were around 18.2 to 18.3mm., which they have been installing with no problem. O.K., I'll use it. I guess the more important factor is how even the spring force is in each of the fingers.

I made up a reaction bar to hold the flywheel so I could go after the rear main seal and the pump cover seal. Before that, though, I stuck on a dial indicator and measured crankshaft end-play. The reaction bar made a good handle to pull back and forth.

The book says it should fall within 0.08mm to 0.15mm (.0031" to .0059"). I was surprised to find mine measured at .06mm or .0023", so it is below the minimum spec. PO#1 said this had not been apart before.

In searching the web, I found this rather curious statement by Snowbum: Click HERE "BMW has specifications on end play, or end-float as they call it, and you need to understand that it varies if oily or dry, and BMW does not tell you about that. The end-float specification is 0.08 to 0.15 mm (which is 0.003" to 0.006"). This is for DRY. If oily, the minimum is 0.15mm (0.006")."

So . . . unless he has a typo here, he is saying that once your crank and related parts have oil on them, the end play should increase to where the dry end play maximum value is now the wet minimum value????

I posted this on the MOA forum some time back and never got a really clear answer. I decided not to worry about being slightly under the low limit, since I know the engine was running this way with no problems. I would worry more if it was at or above the high limit. But . . . I don't quite understand what Snowbum was talking about?

The only other curiosity I found back here was that I believe PO#1 was wrong about the flywheel never having been off before. I'm thinking that there was a service done long ago that he either forgot about or didn't know about.

Clues for this are that the flywheel had a spot of paint near a bolt and a corresponding punch mark on the rear face of the crank. I don't believe the factory marked them for alignment. In fact I read where some people put the flywheel on wrong and then can't find their timing marks anymore. I added a fresh splotch of paint to make the reference mark obvious for my old eyes.

Also, the cover plate on the oil pump is supposed to have four phillips head machine screws. Mine had the hex-head bolts already. It looked to me like the holes in the cover were originally countersunk , but somewhere along the line they had been spotfaced to make seats for the new bolt heads. Fine with me.

The book says that both the inner and outer rotors are marked with a dimple that should face out. Mine only had the dimple on the inner rotor. I marked the outer one with a little ball tipped dremel tool so that I would get it back together as it was with its established wear pattern.

Snowbum says that the original oil pump seal was black and a later one which is a few thousandths thicker is red. Mine already had the red O-ring, and the new one in my gasket kit was the same color.

All the clearances checked good, and there were no obvious signs of wear.

There are many discussions about proper torque for the cover bolts. It's a nasty place to have a leak or to have a bolt work its way out. I used this little exercise as an excuse to spend some of my kid's inheritance and buy a brand new Snap-on torque wrench calibrated in inch-pounds. I already have one of their fancy digital torque wrenches (they call it a Tech Wrench) that switches between NM, Inch-Lb, or Foot-Lb at the touch of a button, but its range is 5 to 100 Foot-Lb, and these bolts would have been close to the bottom of that range.

Torque wrenches are more accurate at their mid-range values. Anyway, that was my excuse. The Snap-on guy happened to be in town and had one on the truck. I got a nice little micrometer style wrench.

Clymer only listed a general value for M6 bolts of 52-69 Inch-Lbs. Snowbum said 88 Inch-Lbs. The FSM shows no special torque, but their general spec for M6 in grade 10.9 is 104 Inch-Lbs, to be reduced by 30% if there is any thread lube (there are arguments whether Loctite acts as a thread lubricant, or if that factor can be ignored). I compromised and ended up using Blue Loctite, torqued to 80 Inch-Lbs.

All said and done, I got out my bigger Tech-Wrench and checked to see what it said. It beeped at the same value without any further rotation of the fastener. I guess I could have used it, but now I have that baby wrench that I always wanted.

Feed the tool fetish!

As in the picture above, there didn't seem to be a lot of oil thrown around in here. I got things pretty well cleaned up:

I changed the rear main seal regardless. You can read for days on end about RMS and the trouble people have had. I found no damage where the old seal had been running. I tracked down some Crocus Cloth and did a little polishing on the flywheel anyway. You have to be a Snowbum devotee or an old fart (or both) to even know what that stuff is. Prepare for blank looks when you ask for it at the hardware store. I got some from McMaster-Carr.

Then I read all the hoopla about how deep to seat the seal. I measured before and after I yanked the old seal. I made sketches. I went crazy obsessing over this. In the end, after all this anal analysis, I used a PTFE seal and seated it to the bottom of the counterbore. I installed the flywheel with no lube on the seal. I buttoned things up with new stretch bolts.

No leaks yet (but that could be on account of no oil in the engine and nothing spinning round).

From there, I kept on with the alloy cleaning till I got everything done on the engine except for the jugs, heads, and valve covers.

My plan there is to pull them off and measure everything (hoping it's all good to go). Then I will make up a plywood base to seal off the spigots on the cylinders. I'll use rubber plugs in the inlet and exhaust ports, seal off the PRT's, etc. With this bolted up as a package (temporary bolts in place of the cylinder studs), I'm going to glass blast it and then perhaps hit the jugs and heads with some Duplicolor DE1612 primer and DE1650 Engine Enamel with ceramic. Those fins are just too deep and close together for me to want to go after them any other way, and the paint might keep the oxide at bay.

This is basically what I did to my CL350, except I used DE1615 as the final coat, which is a slightly different color. This stuff looks good to me and has held up very well. I didn't even bother to bake it and there has been no chipping at all. Here's the little Honda:

In the picture above, the bottom case is polished (as it was originally from Honda), while the upper case, jugs, head, starter motor, and cam case have the Duplicolor paint. The side cover is polished. I'm thinking this might be O.K. on the BMW. I need to see how well the Duplicolor Cast Coat Aluminum matches the BMW engine (or at least the Rub 'n Buff that's on it). One big difference besides the obvious is that the Honda engine came painted from the factory, while the R90 is supposed to be raw.

Throughout all this cleaning on the airhead engine, I kept things sealed up as well as I could to keep the crud from getting inside. Once the rear, top, front, and sides were clean, I tipped the engine up with my sky-hook and pulled the pan.

I cleaned the sludge out of the pan, so the process can start over. There will always be sludge, since BMW did not make the drain plug opening the lowest point in the pan.

Anyway, I got it clean inside and out:

I pulled the suction bell and spacer and cleaned them up -- no cracks and the bolts were tight. The BMW gasket set had this and the new pan gasket included.

I linished the gasket surfaces with some wet/dry (lubed with WD-40) wrapped around a piece of plate glass. Then I stuck the pan back on with four temporary hardware store bolts. That will keep dirt out of the engine for now.

All the exterior bolts, nuts, and washers get bagged, tagged, and labeled in zip lock bags. When the weather warms up, I will bead blast each piece and then take them to a guy to have them re-plated with white cadmium. I roll my makeshift HF blast cabinet outside to keep the residue out of my garage. It's just too cold out there right now.

Looks like I spilled some glass inside anyway.

This setup works pretty well, after a lot of mods to the original HF junk. I have learned not to walk away from it though. One time I had my Triumph jugs in the cabinet to blast the fins. I went inside for a break and heard a big crash. It was windy outdoors and the wind had rolled the cabinet sideways then over on its front. The jugs escaped through the glass panel! Luckily the cylinder block landed in the grass and no fins were damaged.

A friend who was hanging out with PO#2 back in the 90's remembered this Airhead as a running bike. In conversation one day, he told me to be sure and fix the exhaust system -- it used to make a funny chirping noise.

From stuff I've read, that sounded to me like the breather valve making its turkey gobbling noise.

Here's the little devil as found:

The mighty R90 needs more spring pressure than the lesser airheads, so it wears the clip in the lower groove. Here are the bits:

I was determined not to buy a single-use tool to pull this thing out. I'm almost embarrassed to show what I did use, but maybe it will help someone else. This worked O.K.

Searching through the junk bin, I found a bicycle seat post that was about the right diameter. I cut off a chunk; drilled some holes in the side; slotted up to the holes; fitted it around some 3/4" all-thread; pinned it with a 1/4-20 bolt and nut; slipped a 3/4" drive socket over the all-thread; added a couple of jam nuts above the socket (they didn't make it into the picture, but you get the idea); and here is my gen-u-wine homemade gobbler valve slide hammer.

Notice the little trophy it is wearing on the end:

I didn't go to any pains to make it look pretty.

I read that people think the replacement reed valve needs to be carefully oriented. Get it wrong, and the cap won't fit. Also, they say to orient it toward the cap outlet. I spent some minutes staring at this.

I was thinking that both the strap and the screw head would foul the cover. I found out later that was wrong -- only the screw head would be a problem, so long as the valve is seated all the way into the counterbore:

But, I made a reference mark for what I thought was the optimum position. Then I stuck the reed valve in a plastic baggie and put it in the freezer overnight. When I lightly tapped it in the next day, I saw that the top of the strap came out flush with the surrounding surface. A smarter man would have measured this earlier.

I wound up with the valve outlet not quite pointing directly at the outlet in the cap, though I really don't think it would make a difference if it were in there 180° around.

Yeah, that is the first year /6 cover in the picture. I just re-used the one that came on the engine, changing only the valve body itself. (Or did you mean to say it would be better to use the /7 cover?)

I did block the crank. I cast around for a way to do it without putting the front cover back on. I discovered that a special tool I had made to fit the alternator studs on my Triumph also fit the BMW.

It was not an exact fit, but there are three studs in both engines. The difference was that the more robust Lucas system used fatter studs. Since the Beemer studs were smaller and farther apart, they still fit.

I stuck a washer-head M8x1.25 bolt in the end of the crank, stacked on a couple washers, and used my original airhead alternator bolts. It worked just fine:

That left the front end exposed for some more alloy cleanup -- Yippee, it just doesn't get any more fun than that!

Both my bikes have been bead blasted, but this was done as part of a full crank out overhaul. The finish stays pretty good, but I treat it with a spray found in the UK called GT85, which keeps the clean alloy from picking up too much dirt. I was told not to use WD40 on parts that get really hot as is can leave grey staining.

Back in the day it was a very common occurrence for 90/6 s to need new crankshaft and or oil pump seals, might have been a materal problem or a combination of too small Crankcase volume on the big engines. Easy enough to find an oil pan spacer nowadays, but you will have to lower the top cross bar of the centre stand to accolade the extra depth.

This is my first time to use it, but I read somewhere on here that it lasts quite a while. I do know that it will come back off with mineral spirits. I read where somebody bought an airhead and the PO had used Rub 'n Buff. The new owner hated it and was looking for a way to remove it. I suspect that was not Rub 'n Buff. A lot of people scrub aluminum paint into the pores, and that may have been what he had. I tried that, but I liked the Rub 'n Buff better.

Both my bikes have been bead blasted, but this was done as part of a full crank out overhaul. The finish stays pretty good, but I treat it with a spray found in the UK called GT85, which keeps the clean alloy from picking up too much dirt. I was told not to use WD40 on parts that get really hot as is can leave grey staining.

Click to expand...

I guess I should have mentioned that once I got the alloy to where it seemed as clean as I could get it, I followed the WD-40 with some Autosol Aluminum cleaner. Hopefully, if WD-40 does tend to stain on hot parts, this will get around that issue. I don't know, though, why WD-40 would stain. I think it is mostly a petroleum base, like kerosene (paraffin for you Brits).

AutoSol also sells a protective oil that can be sprayed on from an aerosol can once the finish is clean. They are the official polish for BMW, Mercedes-Benz, VW, and Audi, so their stuff ought to work on this old bike.

I'm paranoid about using glass blasting on engine parts, but I do it sometimes with care. I never blast gasket surfaces, combustion chambers, or any surface where oil will flow later. I guess it is commonly done, but it scares me. I have soda blasted all of the above though, with good results. I followed that up with a good scrub in hot, soapy water and a good rinse.

Back in the day it was a very common occurrence for 90/6 s to need new crankshaft and or oil pump seals, might have been a materal problem or a combination of too small Crankcase volume on the big engines. Easy enough to find an oil pan spacer nowadays, but you will have to lower the top cross bar of the centre stand to accolade the extra depth.

Hope this helps, nice bike!

Click to expand...

I've read about that and would like to have a little larger capacity pan, but I hate to mess up the centerstand. It's hard to lift these bikes up by any other means, unless you lift under the crankcase itself. Also, I've read lots of stories about the airhead sidestands and centerstands. I'm looking forward to new experiences if I ever get this bike on the road. :

I read on here (or maybe on the MOA forum) that Craig Vetter is writing a book about his early days, and is looking for the highest and lowest known serial numbers for his fairings, lowers, trunks, etc.

There was a link that sent me to a website about Vetter products. I was surprised to see the comments there from people who are very devoted fans of his stuff.

On most bike forums elsewhere, these things are no longer in vogue. I read here on ADVrider.com someone's post that he tried to sell his fairing on Craigslist. He kept dropping the price, and finally he put it on there for free -- come and get it. When that didn't work, he set it out with the trash, but the garbage man refused it for being too big. Out came the Sawzall!

Like BMW's, Vetter Fairings are an acquired taste. I rode a friend's old Wing once that had the similar Honda fairing and found that it was pretty nice. If I didn't look at the speedo, 90 mph felt a lot like 40mph. There was lots of nice, calm air behind the windshield. Both previous owners of my bike loved the Vetter Fairing, and it's been on there for 40 years.

I have mixed emotions. I want to put my bike back together pretty much like it came from BMW. On the other hand, I certainly won't pitch the take-off stuff. Vetter sold many thousands of these. There must have been a reason why. I also admire him as a person. He is in the Motorcycle Hall of Fame and is still doing interesting things in his retirement.

Anyway, I noticed on that website that the highest known serial number for the first generation Windjammer Fairing was #9161. Out of curiosity, I went and looked at the S/N plate on my fairing. It was #9873, so 712 numbers higher than what they had. I joined their forum and put up my info. Here's the link to my post over there if you are interested. You may need to scroll down to post #29.

At first I got no response, so I bumped them again (post #40 on there). That got Craig Vetter's attention and led to a rather interesting discussion between us. You can see the full conversation by following the above link (you may need to scroll to the next page). I learned that although my fairing had characteristics of the first generation Windjammer, it was actually a Windjammer II. But wait, that wasn't quite right either. It was a transitional model.

This eventually led to the fact that my fairing was the original #1 Test Fairing for the Windjammer II series. In 1973, it was mounted on Craig's fiancée's (now his wife of many years) CB500 Honda. He posted this picture:

That is the very fairing that was on my BMW all these years! I have it stored on a shelf right now.

Some facts that are unique about it: it was the first fairing made from ABS, all previous ones were fiberglass; it was the only one that was never painted because they wanted to see how the ABS held up in weather and sunlight. There were other test fairings, but this is the only unpainted one. It still looks pretty darn good! It is the only Windjammer II that did not have the chrome edge trim (which was made at the Vetter Factory). The trim was not yet ready when this first test fairing was put into service.

In 1974, there was an accident while testing a sidecar with that bike. The Honda was totaled, but the fairing survived. It was spiffed up and sold to a dealership at a bargain.

By coincidence, I learned that the dealership was Sport City Honda in Creve Coeur, Illinois -- the same dealership that sold my CL350 Honda when it was new. Their dealership sticker is still on the back fender. I also bought a new bike there once, which was a 1976 CB550-4. It was the same color as Carol Vetter's bike in the picture above.

The first owner of my BMW bought the fairing from Sport City late in 1974. He installed it himself, and rode behind it out to California, as well as on a couple trips to Mexico.

Here's another picture that Craig Vetter posted on that other forum, showing the aftermath of the accident:

Sometimes, life is stranger than fiction. Who would have imagined anything like this?

Thanks, CafeDude. With what I found out, the fairing is too special to throw away, but I'm not sure I'll ever put it back on. I guess the kids can handle it when they have to clear this place out some day.

Here's the other Vetter part on my Airhead -- the Vetter Rainy Day Fender.

When I first saw this bike, I thought the front fender looked . . . different.

My BMW friends are big into what they call conspicuity. Check out this picture of my FXRS parked between a GS1200A and an R1200RT at night. I took the picture with my camera flash turned on, but the bikes were just parked there with no lights on.

At least my license plate threw back some of the flash:

Also, for people who think Harley's are big, obnoxious machines, compare the size of this 1340 Evo to the behemoths on either side.

Anyway, I figured that's what this fender was all about. It is, but there is more to it:

PO#2 told me that it was aftermarket, but that he had the original fender stashed away. When I bought the bike, I got both fenders. The original has some minor wear and tear scratches from laying around for 40 years, but is basically NOS. It was only on the bike a short while before PO#1 installed the Vetter fender.

I have found out that these things are about as rare as hobby horse poop. A Google search brings up very little info. It will take you to this page where I posted a question about the background story of these fenders. Craig Vetter has said there is an interesting story, but he hasn't put it up there yet (as of today anyway).

Here are some pictures after I removed the fender and cleaned it up some:

Here you can see the vinyl or rubber edging material. It is still in good, flexible condition after 40 years.

Underneath, there is a rubber gutter that starts on either side of the front tip. The gap gets more pronounced further down the fender:

It goes all the way down both sides, catching water flung off the front wheel, until it reaches the flared section at the back. This dumps the water on the road, hopefully keeping it off the front of the engine.

There is some precedent for this style of fender. Velocette had one similar, at least as far back as 1929. Click HERE for a picture. However, I doubt they had the rubber gutter.

I plan to use the original BMW fender, but I may regret it. Of all places to put the ignition points on a motorcycle, directly in the slipstream of the front tire is not high on the list. (I realize they had to drive the points off the front end of the camshaft, but geez!)

At least they're sealed up well, right? Wrong. They are behind a louvered front cover and then sort of protected by a very iffy fitting strip of rubber. This strip of rubber then has a gap in its upper left corner to let the wire (and water and dust) in to the points. Once the water is in there, it has no weep hole to exit. There are stories of unpleasant experiences because of all this.

I hope nobody is offended by my comments about BMW. I'm just adding my first impressions as I learn about my first Airhead. I'm in it for the duration, regardless.

So, on to the front of the engine. I was not going to pull the timing cover, figuring that the chain and sprockets were probably good with only about 40K miles. I decided that was stupid, so off it came.

I changed the crank and cam seals and was about to replace the tach drive seal when I found that it was not part of the gasket set. Neither was the strip seal that surrounds the points cavity.

Here again there are lots of stories about this strip seal. It is easy to dislodge, it comes out fairly easily. Disston favors insulated copper wire, which is probably better than the original. Whiteguyphil used a piece of screen door tubing that looked good too. The original seal is, I believe NLA -- at least Bob's BMW lists it as such.

I got curious as to how the front cover meets the seal. How thick should the seal be, and how wide? I did some searching on-line but didn't find anything. So, I put some blue tack in the groove and put the front cover in place, then removed it, kind of like checking piston to valve clearance.

On my engine, there is uneven fit around the cavity. At the bottom, the cover does not sit on the full width of the seal, only on the lower half of it. The cover would tend to push the seal upward and into the cavity. The left side fits pretty well, while the right side is again rather off. I'd call this a design flaw, complicated by casting quality issues.

A round seal, like Disston's wire would work better than what came from the factory, but I think I'd like something that really started out as a seal. The guy at Bob's BMW told me that their shop uses an oil filter O-ring from a K75 for this application on airheads. They cut the length to fit. So I ordered one -- part number 11131460425. It's here, but not installed yet.

If anyone is looking for this, I found you can't search by part number on Bob's fiche and have it come up to put into your shopping cart. You can get to it by going through the fiche for: K75; engine; oil pan; item# 5 oil seal

It is 3mm x 88mm, so with a little math it works out to be 276mm circumference. About 200mm is enough to go around the points groove.

A closer look at the fit:

Then there's the timing chain and sprockets. The engine is out, and I can tilt it so the front face is horizontal.

It would seem like a good idea to change the sprockets and chain, but I think the old ones would run a while yet. I can stare at the profile and think that the cam sprocket teeth look to be about the same condition as the crank sprocket teeth.

They are supposed to wear more on the left tooth profile. Maybe they are and I don't see it.

People often change the crank sprocket and leave the cam sprocket alone. To me the tooth condition looks about the same on both. If there is wear on the cam sprocket at all, wouldn't that accelerate the wear on a new chain?

Here's what they look like. The teeth aren't worn to sharp edges yet. They all have a land at the tip. The cam sprocket:

The crank sprocket:

The tensioner:

Since the tensioner is wider than the chain, I would expect a groove in the middle of the pad if it had a lot of wear. This one looks the same all the way across.

The crank nose bearing feels brand new to me.

I can grasp a chain pin midpoint around the cam sprocket and try to lift it from the tooth space. It doesn't move, so the chain must not be worn too badly.

It would be great if someone had a brand new set of sprockets and traced their profile on a piece of paper with a fine pencil or pen. They could put up a .pdf that the rest of us could print out, cut out, and lay onto our sprockets to compare the profile of the teeth and spaces. Otherwise, it seems like an eyeball W.A.G. Anybody know of such a thing?

I'm on the fence about changing these, and would sure be open to opinions.